Photoelectrochemical properties and photodegradation of organic pollutants using hematite hybrids modified by gold nanoparticles and graphitic carbon nitride

Abstract

In this study, heterojunctions of gold (Au) nanoparticles with three different average sizes (26, 20, and 12 nm in diameter), graphitic carbon nitride (g-C3N4) sheets, and rhombohedral hematite (Fe2O3) hybrid photocatalysts were fabricated via sonication at room temperature and used in the degradation of rhodamine B (RhB) dye under visible irradiation. The Au sensitized g-C3N4/Fe2O3 hybrid photocatalyst using 12 nm-sized Au particles, exhibited apparent rate constant of 31.6 x10(-3) min(-1), nearly 19-fold higher than that of pure hematite (Fe2O3 = 1.7 x 10(-3) min(-1)), and higher than those of the other hybrid samples. The superior performance of the Au/g-C3N4/Fe2O3 hybrid was attributed to a potential energy level difference, high optical absorbance, and the effective separation of photogenerated charge carriers. Additionally, the Au sensitized g-C3N4/Fe2O3 hybrid using 12 nm-sized Au particles, showed the highest specific surface area (46.5 m(2) g(-1)), compared with that of pure Fe2O3 (5.5 m(2) g(-1)) and g-C3N4/Fe2O3 (29.7 m(2) g(-1)) hybrid photocatalysts, showing numerous available sites for dye adsorption and degradation. Moreover, the transient photoresponse and open-circuit voltage decay clearly showed a high photocurrent and longer charge carrier lifetime, respectively. Reusability tests confirmed that the Au/g-C3N4/Fe2O3 hybrid photocatalyst was highly stable and recyclable. Hence, the work presented demonstrates the efficient, stable Au/g-C3N4/Fe2O3 hybrid photocatalyst for degradation of toxic pollutants under visible irradiation. (C) 2015 Elsevier B.V. All rights reserved.